Sun Science

By Robert Perkins

Photographs by Dietmar Quistorf

Space Sciences Center director Darrell Judge in a cleanroom where he and his researchers assemble extreme ultraviolet spectrophotometers – detection instruments that measure short-wavelength ultraviolet radiation from the sun. He stands alongside part of a rocket payload that will carry these detectors to an altitude where their view of the sun will be unobscured by atmospheric gases.

SSC was founded in 1978 by Darrell Judge, who is still the center’s director, with the goal of recruiting top-notch scientists to academia and offering new frontiers of research opportunities to both professional scientists and students. It can be hard for universities to compete with the financial perks and exciting research and development opportunities of the private sector. But multidisciplinary research at a major research university such as USC can prove appealing.

Currently, Judge – a professor of physics and astronomy at the USC Dornsife College of Letters, Arts and Sciences, and an expert in spectroscopy – leads half-a-dozen research faculty and non-faculty on projects that study the sun. They use special instruments designed by SSC and built at the machine shop in Kaprielian Hall.

“We develop all of our own instruments,” says Judge. “They are cutting-edge. That’s where SSC has been a leader.”

Backed mostly by NASA funding, SSC sends solar-observing instruments into space every few years at White Sands, N.M. The next launch is scheduled for July.

Carried by Canadian-built 50-foot rockets, the instruments reach a height of about 300 kilometers – roughly the altitude of the International Space Station, and three times the target height for the student-run Rocket Propulsion Laboratory’s Traveler rocket. SSC also has piggybacked instruments onto two satellites currently in space.

Free from atmospheric interference, the SSC-developed specialized cameras on board take snapshots of the sun in the short-wavelength region of the electromagnetic spectrum.

In 1995, an extreme ultraviolet (EUV) radiation monitor designed by SSC scientists was launched with the Solar and Heliospheric Observatory (SOHO). Rather than placing the satellite into orbit around Earth, the SOHO team positioned it at the “Lagrange Point” – a point between the sun and Earth where the gravitational pull from each body is even. From this stable position about a million miles from Earth, the SSC monitor transmits precise data about the highly variable EUV radiation from the sun.

EUV radiation has numerous negative effects: It is absorbed in Earth’s upper atmosphere and generates heat. It affects non-satellite radio communications by scattering radio waves and causes radio blackouts at certain frequencies. EUV can also be harmful to astronauts and satellites, making it even more important for scientists to track.

A second EUV instrument package was launched with the Solar Dynamic Observatory last February as part of NASA’s Living With a Star program. The mission’s goal is to better understand the complex physical processes at work within the sun – with the hope of one day predicting how and why solar variations affect life on Earth, particularly their impact on human technology.

A few years before founding SSC, Judge led the team that designed the ultraviolet photometers carried by Pioneer 10 and 11 – the first space probes to travel to Jupiter and Saturn and then leave the solar system to explore the local interstellar medium. These spacecraft famously also carried a 6-by-9-inch gold-anodized plaque featuring a pair of nude human figures and various other symbols, intended as a message to any intelligent life that should chance upon it. The Pioneer probes are now about 10 billion miles from home (100 times the distance from Earth to the sun). They will never return to our solar system.